Iron ores are present abundantly, and high-quality iron ores containing small amounts of impurities including sulfur have been used in large quantities. However, the demand of iron ores has increased and it is becoming difficult to procure high-quality iron ores. Therefore, it is necessary to purify and then use low-quality iron ores containing large amounts of impurities including sulfur.
Known as a technique for diminishing the impurities contained in low-quality iron ores is flotation. Flotation is a process for beneficiation in which air bubbles are supplied to an aqueous suspension containing fine iron ore particles, and particles of a specific kind only are caused to adhere to the air bubbles and selectively float and are thus separated.
When the sulfur, among the impurities contained in low-quality iron ores, is selectively removed, a xanthate is generally used as a collector. For example, Non-Patent Document 1 discloses a technique in which pyrrhotite (substance represented by FeSx) containing 36.73% sulfur is subjected to flotation using a xanthate as a collector. Non-Patent Document 2 discloses a technique in which pyrrhotite containing sulfur in the range of 39.0-42.5% is subjected to flotation using a xanthate or RADA (Rosin Amine D Acetate) as a collector. Furthermore, Patent Document 1 discloses a flotation technique in which a xanthate that has been reacted with a carbohydrate is used in combination with an amine and the pH of the aqueous solution is adjusted to about 8, thereby heightening the iron concentration of taconite, which is a poor ore, from about 30% to about 60%.